In this field there are known a number of proposals such as those of the documents EP 0878332, WO 2006/032669, US 2007/0257570 and WO 2007/083209.
In the present application, the expression “motorized hub” is used to designate the mechanical assembly comprising the hub, the hub-carrier, the system for guiding the hub relative to the hub-carrier, the electric motorization and the braking means of the hub. The motorized hub is thus intended on the one hand to receive a wheel equipped for example with a tyre and on the other hand to carry a vehicle, generally via suspension means. In the present application, the expression “motorized wheel” is also used to designate the mechanical assembly comprising the motorized hub defined above and the corresponding wheel.
One of the difficulties with adopting such motorized hubs on mass-produced vehicles is backward compatibility with solutions already adopted and validated by manufacturers for some components such as suspension systems and wheels. Another difficulty is obtaining a compact and simple system that is as light as possible in order to render the cost acceptable to the automobile industry.
In particular, integrating electric motors in the wheels is particularly desirable because the adoption of electric traction often entails the necessity of carrying batteries to store electrical energy which, even with the best performing technologies known at present, makes it obligatory to devote a sufficient volume to the batteries on board the vehicle unless the range of an electric vehicle is enormously reduced. Similar reasoning may be applied in the case of fuel cell vehicles.
Moreover, if it is wished to be able to develop a sufficient traction torque, it proves necessary to install reduction means because it is not possible, with a sufficiently compact electric motor, to develop a torque appropriate to drive a motor car directly.
Finally, it is generally necessary to be able to integrate into the wheel not only the electric motor and the associated reduction means but also a mechanical braking device (disc or drum brake).
In most known arrangements, the disc or the drum and the electric motor are concentric with the wheel.
Although interior rotor motor configurations where the motor axis is offset relative to the axis of the wheel to enable a reduction stage to be installed between the axle of the wheel and the rotor of the electric motor would seem to have the only benefit of installing a sliding system providing the suspension of the wheel also integrated into the wheel, the applicant has noticed that sufficient space may be freed up to install a brake disc or drum radially inside the shaft of the motor and axially on the vehicle interior side relative to the reduction means.
This represents a good compromise, given in particular that a portion of the braking torque may be provided by electrical means.